SMA AND LTT HAVE NMAC WHEN LNDG ON RWYS INTERSECTING AT THE THRESHOLDS.

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THE BASIC PROB WAS 2 ACFT LNDG AT AN UNCTLED ARPT WITH MARGINAL WX CONDITIONS AND 1 ACFT IFR AND THE OTHER ACFT VFR. THE VFR ACFT; WHICH I WAS FLYING; DID NOT HAVE FAA RADIO COM CAPABILITY. I DID HAVE RADIO COM WITH MY OFFICE PERSONNEL VIA A BUSINESS BAND RADIO. IT'S A 5 MIN FLT FROM MY AIRSTRIP TO THE MITCHELL ARPT. UPON DEP FROM MY PVT AIRSTRIP; MY OFFICE PERSONNEL CONTACTED MITCHELL AWOS AND THE WX WAS RPTED TO BE 1000 FT CEILING AND 4 MI VISIBILITY. THIS INFO WAS RELAYED TO ME AT XX50 HRS. UPON ARR AT THE MITCHELL ARPT; THE ROTATING BEACON WAS NOT OPERATIONAL INDICATING VFR CONDITIONS DID EXIST. I ENTERED THE TFC PATTERN AND LANDED ON THE THRESHOLD OF RWY 35 AT APPROX XX55 HRS. UPON ROLLOUT; AN LTT LANDED ON RWY 30. BOTH ACFT LANDED ON THE ARPT AT THE SAME TIME. THE LTT MADE AN INST APCH TO RWY 30 AND I MADE A VISUAL APCH TO RWY 35. IT'S THE AGE-OLD PROB OF 1 ACFT VFR AND 1 ACFT IFR. THE IFR ACFT IS DEPENDING ON SEPARATION BY RADIO AND THE VFR ACFT IS DEPENDING ON VISUAL SEPARATION. MARGINAL WX CONDITIONS CONTRIBUTE TO THESE SITS. AT XY05; I CALLED MITCHELL AWOS BY MOBILE TELEPHONE AND THE WX WAS RPTED AS 1100 FT CEILING AND 3 MI VISIBILITY. ONE HAS TO BE EXTREMELY VIGILANT WHEN LNDG AT AN ARPT UNDER MARGINAL CONDITIONS WHEN THE VISIBILITY AND CEILING PERMIT VFR LNDG AND; AT THE SAME TIME; ACFT ARE MAKING INST APCHS.